In what has been one of the worst kept secrets in royal circles, the Keeper of the Privy Purse will assume his new role after the Queen’s golden jubilee celebrations next August.

Sir Michael will arrive at St James’s Palace with the reputation of having brought the Queen’s budget under tight control, and it is likely he will use his talents to boost income from the Prince’s Duchy of Cornwall estate, famous for its organic produce.

A former partner at KPMG and great grandson of the founder of Peat Marwick, Sir Michael joined the palace in 1990, becoming Keeper of the Privy Purse in 1996.

Confirmation of his departure will fuel speculation about a likely successor.

Earlier this year Gerry Acher, a senior Partner at KPMG, was appointed as honourary treasurer for the Queen’s jubilee celebrations committee, chaired by P&O chief Lord Stirling.